A lot of small red dots on the back may be caused by acne, folliculitis, allergy, eczema and so on. 1. Acne: Usually a lot of small red dots on the back may be related to acne, especially for teenage patients, more androgen secretion, coupled with dietary intolerance, may lead to back acne. 2. Folliculitis: small red dots may also appear after bacterial infection of the hair follicles on the back of the patient, usually related to excessive oil secretion. 3. Allergy: Usually when the patient touches or eats substances that are easy to cause allergy, a lot of small red dots may also appear on the back. 4. Eczema: small red dots on the back may also be related to eczema, usually accompanied by itching, oozing and other phenomena. There are many other reasons why there are many small red dots on the back, so it is recommended that the patient go to the hospital. After a clear diagnosis, follow the doctor’s recommendations for treatment.